Wireless Key Refreshment Using Session Count for Battery Management

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Solution Overview

Problem

In wireless battery management systems, periodic key refreshment is challenging due to synchronization complexities, leading to increased system cost and reduced throughput and latency, while existing solutions struggle to ensure forward and backward secrecy and prevent nonce-key pair reuse.

Innovation Solution

A key refreshment technique using a session count is implemented, where a new network key is derived during secure sessions based on a pre-shared key and current network key concatenated with a session count, allowing for on-the-fly key refreshment without interrupting data exchanges and reducing unnecessary key exchanges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If periodic key refreshment is implemented to ensure security, then forward secrecy and backward secrecy are improved, but system complexity and synchronization overhead increase

Engineering Contradiction:

Improveforward secrecyVSAvoidsynchronization complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Each node independently derives the session key using the key derivation function with the pre-shared key and its own session count, eliminating the need for centralized key distribution and reducing synchronization complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The session count parameter is incremented by each node to generate different session keys over time, enabling periodic key refreshment while maintaining simple synchronization through a single counter parameter

Inventive Principle:

Principle #35Parameter changes

2Reliability

If all nodes are synchronized to use the same session key, then security consistency is improved, but overhead and system cost increase

Engineering Contradiction:

Improvesecurity consistencyVSAvoidcommunication overhead

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

Nodes independently compute session keys using the same key derivation function and their local session counts, achieving security consistency without requiring key distribution communication

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The key derivation function serves multiple purposes: establishing initial security, enabling periodic key refreshment, and ensuring all nodes derive consistent keys, replacing multiple separate key management operations

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If key refreshment is performed frequently to prevent nonce-key pair reuse, then security is improved, but throughput and latency are reduced

Engineering Contradiction:

Improvenonce-key pair uniquenessVSAvoidnetwork throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Data communication and key refreshment operations proceed simultaneously without interruption, as each node independently derives new session keys while maintaining ongoing data exchanges, eliminating downtime and preserving throughput

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS20250016557A1Key refreshment with session count for wireless network

Publication Date: 2025.01.09 TEXAS INSTRUMENTS INC

AI summary

A wireless interface includes: network formation circuitry configured to establish a wireless network between a primary node and a secondary node; data exchange circuitry configured to perform data exchanges between the primary node and the secondary node using secure sessions; and key refreshment circuitry configured to derive a new network key for the network based on a pre-shared key and a current network key concatenated with a session count. The new key is derived during at least one of the secure sessions.